Adsorption process and apparatus



March 20, 1951 D H lMHOFF 2,545,850

ADSORPTION PROCESS AND APPARATUS Filed Nov. 26, 1945 5 @5550 l l f-5%@ jf INVENTOR -Jmw/M ATTORNEY ByfuM/g Patented Mar. 2o, 1951 UN fl TED lTAT RAT-TENT OFFICE ADS'ORETION 'PROCESS AND PPARATUS Donald n. Imho'fn ALong Beach, :'Ca1if.,zassign0r Lto Union Oil Company of California, `.Los -An- ,'geles, `:Ca-lif., a corporation iof `-California Application November 26, 1945,SerialiNof6305905 This invention relates 'to the separation of Vgaseous mixtures iby selective adsorption of cer- "tain of lthe fcomponentsc'f .such Amixtures lonso'lid -adso'rben'ts and applies particularly `to the sepa- 'rati'on of gaseous mixtures vcomprising hydrocarbons by selective adsorption on granular :charcoal Gaseous mixtures containing `valuable -hydro- -carbons fin admixtures with flue gases fin large :amounts are encountered iin 'many processes, such as for example cracking process "for the production .of lotw boiling hydrocarbons. 'Modiications of :conventional :adsorption 'processes `can be used to extract the bulk aof .the .normally .liquid hydrocarbons rand teven a large proportion `of "the C4 hydrocarbons, but tit is generally 'uneconomical tto operate :at .'suiiciently high pressures for fsiiliciently low temperatures lto re- :cover :any Isubstantial proportion of the v'C2 'and -C3Jhydrocarbons, which :may contain ta high :proportion of .potentially `Valuable .ol'e'lns, V'such as ethylene, propylene, acetylene, an'd athe lik'e, `which are Jeither wasted or employed "as low- -value .fuel gas.v VThe present 'process is ":particu- .larly applicable 'to the .separation of 'normally gaseous .mixtures and particularly Agaseous '.m'ixtures of `hydrocarbons .containing five carbon atoms f-,or less.

Itis known `vthat certain 'solid va'dsorb'ents .such as 'for example activated `charcoal 'for silica fgel will :adsorb some :gases such as waiter vapor, 'benzene vapor, butane andthe like more readily than they will other gases, such as h'ydro'gen, n'itrogen, :methane .and the like, Aand that by heating `the 'enriched adsorbent 'containing fthe adsorbed :gasesth'ese gases :may be :liberated sub- 'stantially completely :and the adsorbents affiner fb'ein'g cooled 'again are capable of 'further Aselec- 'fciv'e adsorption. "This :has @led to the develop- :ment fof various processes rior the .separation .of rgases involving y:adsorption on solid 'adsorbeiita Yheating 'the enriched adsorbents 'to liberate 'the adsorbed gases and lcooling the thus 'regenerated .adsorbent for `further use. 'The present invention 'involves Ia vprocess v10T this type lwhich constitutes an improvement'oyer any previous :procfess described in fth'a't it :aftords greater 'eliciency lof `'separation 4as well as greater `simplicity fand -economy lof operation.

- general 'the process of separating "gaseous lmiXtures by 'selective adsorption on fa granular adsorbent involves the steps of countercurrently -adsorbin'g certain ieomp-onen'ts of 'the gaseous mixtures fin va bed fof charcoal, or v'other adfsor'bent, preferably `in a moving 'bed foi 'charfcoal, 9.the femfi'ched =or saturated charcoal :flowing :from the adsorption :zone through :one or :more 'rectification zones as hereinafter described into a stripping fsection wherein "the .gaseous components 'are yfdesorbed from the :charcoal by means .of heat .and steam :or y:other Vvstripping gas. Erom 1,the stripping section .the .charcoal passes :through ."a 4sealing vleg `finto 2a rconveying system vwherein it is scarr'ed fto :the @top of the -adsorber andi-from thence through -a 'cooling vsection back into the adsorbing `section to complet-e 'fthe ioycle.r

lVarious modifications Imay -rbe 4:employed which are fdescribed in `:greater zdetail hereinafter.

Thus in the conventional .process of selective adsorption, a gaseousfraction such as a hydrocarbon traction .is tdivided into 'two separate ,fractions "one fenriched =in higher :molecular weight components and .the other enriched in 'the lower molecular .weight components, ,the lforrner'being obtained as the Vadsorbate from the stripping :section and the flatter, passing through the :adsorption section, lbeing preferentially desorbed Eby the lhigher l-molecular weight components.

fI-n a recent improvement vin 'the art .of y.selective adsorption -a-nd separationof gases, the ad- 4sorption Pcolumn has ibeen provided lwith two or more frectcation sections whereby it is ,possible ythrough the. usage -of relluxing to obtain from a gaseous Atraction :not only -a :lean gas and -an :adsorbate by `one or more :heart cuts, fi. e. fractions -.of :relatively Anarrow boiling range 'separated `.from Aa wide Aboiling range hydrocar- Lbon fraction. In the :resolution of fa normally gaseous hydrocarbon :fraction containing -for example C1, C2, C3, :and -C4 olefms fin fa conven- Itional selective adsorption -process employing fa solid igranular adsorbent, 'fit yis possible 'to fresolve f two compon'ents;v fone enriched `in the v:higher molecular weight ."hydrocarbons and the lvother vzvcarbons, the dividing point 'being a `-function oi the ratio :of :charcoal Vand feed :'stock, 'charcoal flow1rate, :and P:the like. In `the Pimproved -fh'eart v'cutting process, the heavier components such fas (Cz, TCG, and gC4 paraiiins fand olefms .are adfsorbe'd 'iby @the .fsoli'd adsorbent iin :an :adsorption Asection fof A'the lcolumn, the adsorbent thereafter passing through :a xnumber :of 'rectiiying'fsections iwhere'in it isfrsubjfec'te'd to a nfeiiux of"'C3,Par1dfC4 hydrocarbons, `for example, "which reflux :has Tthe effect of -de'sorbing the Cz paraln's 'and :oleiins which may be removed irom lthe Icolumn `by 'approp'riate rm'eans as a heart cut from "the wider range ieed stock.

tofore possible.

and rectification 'zones of the apparatus.

tubes, or alternatively the adsorbent may be stripped in the process of 4conveyance back to the initial stages oi" the operation. Either of these processes possess inherent disadvantages paramount among which is the limitation of the amount of stripping gas which may be employed as a result of the diminished effective diameter of flow of the adsorbent through either a tubular stripping section'or a gas lift conveyance system. The effect of the limitation of the quantity of stripping gas which may be employed is to increase the required temperature of stripping in order to obtain satisfactory removal of the hydrocarbons from the adsorbent 'inasmuch as this removal is a function of the two variables of temperature and quantity of stripping gas. Thus the lower the permissible rates or stripping gas the higher the required temperatures for a given degree of stripping and the higher these temperatures the shorter will be the'eiective life of the adsorbent due to increased polymerization, etc., of the 'hydrocarbons present on the adsorbent.

It is an object, therefore, of the present in- Avention to provide animprovement in the art of selective adsorption and more particularly an improvement in the eiciency and economy of the stripping of the adsorbed components of the gaseous feed from the adsorbate. Correlatively, it is a further object of my invention to provide an apparatus for the selective adsorption and separation of gaseous mixtures wherein the recovery of adsorbed components from the adsorbent is accomplished more efliciently and economically than has been here- These objects are attained according to the present invention through the usage of a new type of stripping section so designed as to premit exceedingly high rates of stripping gas flow with a corresponding reduction of required stripping temperatures. The us age of higher rates of stripping gas iiow is made possible by the inclusion in the stripping zone of the adsorption process of an additional section 'beneath the externally heated tubular section which additional section provides substantially 'the same cross-sectional diameter of eiective charcoal iiow as the adsorption and rectiication` sections of the system, thus permitting usageof stripping gas rates greatly above those possible through the tubular stripping section.

In the conventional tubular stripping section the cross-sectional diameter of adsorbent iiow may range from as low as to not more than 50% of the diameter of iiow in the adsorption This restriction in ow diameter is necessary in order to permit the effective heating of the charcoal by means of flue gas or the like, but at the same time this restriction reduces the quantity of stripping gas which may be used proportionately to the degree of restriction. By the addition of -a larger diameter stripping section -beneath the tubular section into which the adsorbent, heated in the tubular section, iiows, it is possible to put through this lower section, having a iiow diameter substantially equal to that of the adsorption and rectication zones, a quantity of stripping gas from to 500% greater than through the tubular section. Thus stripping gas such as steam is introduced in the lower portion of this additional section by means of a suitable engager such as a tube bundle or the like, is caused to flow through this section countercurrently to the adsorbent and the major portion of the stripping gas is removed from the upper portion of the section while a relatively small portion is allowed to continue upwardly through the tubes of the tubular section of the stripping zone.

The present invention may be more readily understood by reference to the drawing in which apparatus is shown in vertical cross section wherein the selective adsorption of a gaseous mixture may be accomplished. Such an apparatus may be employed for the separation of any gaseous mixture by selective adsorption on a suitable adsorbent such as granular charcoal and for the sake of convenience the process will be described in relation to the separation of a gaseous mixture comprising C1, C2, C3 and C4 para-mns and C2, C3 and C4 olens which may or `may not contain small amounts of lighter and heavier gases.

Referring to the drawing, the feed gas is introduced to the adsorption section II of adsorption column I0 by means of line I2 controlled by valve I3 and is distributed within the adsorption section Il by means of disengager I4. A solid bed of granular charcoal is caused to flow downwardly through the adsorption column at such a rate in relation to the feed rate that substantially all of the ethane, ethylene and heavier hydrocarbons are adsorbed by the charcoal in the adsorption section l! while the methane and any lower boiling gases which may be present pass upwardly therein and may be withdrawn from the adsorption section by means of line I5 controlled by valve I6 passing through line Il into the vent line I8. Alternatively and by means of valve I8, the amount of lean gas withdrawn from adsorption section Il'may be controlled so as to force the passage of a portion of the lean gas through the tubes of the vcooling section immediately above as hereinafter described.

The saturated charcoal passes from adsorption section II through disengager I4 into the rectification section I9 wherein equilibrium is established between the methane and lighter gases which may have been adsorbed, and the Cz and heavier hydrocarbons by refluxing the charcoal with C2 hydrocarbons which are desorbed from the charcoal at a point lower in the column. Thus, in the rectiiication section I9, any residual methane or lighter gases which may have been adsorbed by the charcoal passing downwardly through disengager I4 are desorbed by virtue'of the selective adsorption exhibited by the charcoal for the C2 hydrocarbons in relation to the methane which are caused to pass upwardly through disengager 29 into `rectiiication section I9. The

` desorbed methane and lighter gases then passupcoal-is remixed with the heavier components, in

the teeth. i. e.C3 and C@ hydrocarbons to effect the desorption of the. C2 hydrocarbons the level of Cc.. C4 ren-ux being controlled at a given point within the rectihcation section 2| by utilization ot the temperature rise within the section resultfrom the` heat ot adsorption of the. C3 and C4 hydrocarbons. By injecting, or otherwise introducing Cs and C4 hydrocarbons into the rectication,Y section 2l to.4 serve as reflux there-in the. C2 hydrocarbons: are desorbed due tothe preferential adsorption of the heavier hydrocarbons, andthe desorbed C2v hydrocarbons flow upwardly in the section whereby a portion of the C2 hydrocarbons may be removed from recti-ncation section 2| by means of line 22v controlled by valve. 23.. The remaining portion of the C2 hydrocarbons. are caused to pass upwardly through disengager 20 to insure. a continued retention on the charcoal owing downwardly fromv rectification section |'9 of the: heavier hydrocarbon components. In this manner a heart. cut is obtained comprising com.- paratively pure ethane and ethylene.

The charcoal substantially free of the C2 hydrocarbons and lighter gases passes from rectification section 2t through disengager 2% into the stripping zone comprised of the tubular stripping section 2,5 and the large diameter strippingsectiony 26 disposed beneath the tubular section of the stripping zone. The charcoal passing through disengager 2t passesr downwardly through thev stripping tubes which are heated externally by means' of tluegas introduced by 21 controlled by valve Z3 and removed from the section by line 29 controlled by valve.y 3i).

yFrom the tubular section charcoal hows through disengager 3i into the large. diameter section 26. Steam is; introduced to7 this section by means of line 32 controlled by valve 33 and is distributed Q A large portion of steam introduced into the large diameter stripping section is removed Y therefrom by means of line 35 controlled by Valve through the section by means of disengager 34. .to

Due tothe large diameter of this section in comparison to that of the tubular heating section .immediately above, it is possible to4 lintroduce .quantities of steam greatly in excess of the amounts which could be introduced directly to the tubular heating section. This large. quantity of steam nowing countercurrently to the charcoal through section 2.6 has the effect of stripping the hydrocarbons from the charcoal at temperatures considerably lower than. those required it smaller steam rates are. employed. The temperatures necessary for effective stripping of thead-sorbent, in this case charcoal, are a function not only of the rates of ow of the stripping gas but also of ,the char-"materV ot the gaseous. components adsorbed on the charcoal. However', in a light hydrocarbon fraction such as employed in this description, the tempera-ture ot stripping ina conventional tubular stripping section such, as

.the tubular heating section 25 as shown in thel drawing, is in the neighborhood of 500 or higher, while by employing the large diameter stripping section in conjunction with the: tubular heating section according to my invention, it is possible as a resultv of higher steam. rates to. accomplish the same if not more. eifective stripping ata temperature of from da F. to 400- F. Advantages. of lower temperature strippingl are. immediately apparent to those skilled in the. art

.large quantities of charcoal to temperatures as .oigo as soir e.

3d while the remaining portion is caused to ow upwardly through disengager 3| and the tubular heating section -25 and is removed therefrom together Awith the hydrocarbons de sorbed by means of line. 3T controlled by valve 38. The large quantity of ,steam removed fromthe lower, large diameter section contains only a relatively small amount of comparatively heavy hydrocarbons and asa result a large proportion of the heat may be recovered in an evaporator provided. with an aspirator. Such recovery of the. sensible heat is impossible from the steam passing through the tubular section of the stripping zone because of the lighter hydrocarbons present therein.

Thesteam is then. removed from the desorbed hydrocarbons` obtained from lines and 31 and a portion o-f these hydrocarbons is. reintroduced to rectification section 2l by means. of line 39. controlled by valve 40 and function therein as re'ux as described above.A Alternatively valve 3.8 on make gas line 3l may be so .controlled as to force a portionof the. steam hydrocarbon mixture to flo-w countercurrently to the. charcoal through disengager 24 into the rectication section 2| in lieu oi the externally introduced redux. However,.1 have found the. refluxing action to be more eifective if the steam removed from the. hydro- :carbone prior to introduction of the latter into the rectification section.` l The charcoal passing through the stripping zone, i.- e., tubular heating section 25 into the large diameter stripping section 2li passes through disengager 34 into the lower portion of the column at which point thev rate of vflow of the charcoal is most conveniently controlled. Any desired manner of controlling thisv flow may be employed such as the charcoalfeeder 4|, as shown., or the like. The charcoal. passes through the. feeder it into the sealingleg'" 42, the length of which is `dependent upon the type of feeder or ow regulator-employed. In the drawing a level control .12:3- is-'shown whereby the length of the sealing ,leg may be keptat a minimum by virtue of the fact that the charcoal is maintained in the seal- The charcoal released by the level control 43 ows through transfer l-ine 4d into; the gas lift system 4.5v and by means of gas lift system d5', the charcoal is conveyed to the charcoal gasseparator 48g from whenceV it ows into the hopper d1 at the top of adsorption column iti. A portion of the gas flowy ing through-the gas lift system t5 is allowed to -pass countereurrently to the charcoal through transfer line 44 in order to sweep any residual steamtrom the charcoal from whence it passes .via the steam vent. line 48 into` condenser 49.. In condenser 49" the steam is separated'from.A the .lig-ht- Vgases which are passed: through line 5% to .the vent 8;.

" rovedfrom hopper 4l byY line. 5| may be passed 'through valve 54. into the vent line I8. The charcoal from hopper 41 which may still be comparative-ly warmpassedi therefrom into cooler .55 which-may be comprised'- of a tube bundle such as. found inthe tubular heating section 25e. A

.portion of the lean gas from the adsorption section H may be caused to.- tlow countercurrently 'to the charcoal through the cooling tubes in cooler 55 as described above and thence through hopper 4'.' and outlet line 5 l Many modifications in the operation and in the Idesign of the adsorption unit may be employed without departing from the present invention which comprises an innovation in the art of selective adsorption whereby two sections are pro- -Vided in the stripping zone; one a tubular heating section and the other a large diameter principal stripping section. For example it may be desirable to split the operation separating the process of adsorption and stripping into two separate columns wherein, as in the above-described example, the heart cut will be obtained in the initial column by introducing the heavier components obtained in the stripping column as reflux to effect the desorption of the intermediate components. Whereas, the adsorption process is described with reference to a modified procedure wherein a heart cut is obtained from the gaseous feed, it is to be understood that the present invention pertaining to an improved method of stripping is not in any way dependent upon the usage of this modified adsorption process and it is as equally effective when the process involves solely the adsorption of certain components from a gaseous mixture followed by the subsequent recovcry of the adsorbed components from the adsorbent by stripping action. Y

One modification of the adsorption process which may be employed Without departure from the principles of the present invention is the use of an elevator type charcoal conveyance rather than a gas lift system as described. In such g, case the charcoal flowing through transfer line 44 would be lifted directly by bucket conveyor and deposited at the top of the column, or if two column operation was employed the enriched charcoal flowing from the secondary rectification section or from the adsorption section in the case of simple selective adsorption, would be transferred by an elevator to the top of the stripping column A, which according to the present invention, would be comprised of a tubular Vheating section and a large diameter principal stripping section.

Whereas, I do not intend to limit the usage of the improved stripping of my invention to charcoal adsorption inasmuch as it finds application in any adsorption process, charcoal is the preferred adsorbent particularly for the separation of hydrocarbon gases. The charcoal employed in the above process is preferably granular, about 10 to 20 mesh although sizes as large as about 4 mesh and as small as about 100 mesh may also be employed. By charcoal herein is mean carbon or animal or vegetable charcoal and the like, although an vactivated form of carbon or' charcoal is preferred. After long usage small amounts of highly adsorbable materials may accumulate in the charcoal and hamper its eiiciency although by means of the improved stripping as herein disclosed the charcoal will retain its eiiiciency over considerably longer periods than were heretofore obtainable. However, if such impairment occurs the charcoal may be withdrawn from the column and may be reactivated by high temperature steam treatment.

' The process of this invention may be employed for the separation of any mixture of gases containing one or more components which are more readily adsorbable on the charcoal or other adsorbent than another component into two or more fractions depending upon the number of components in lthe feed and the particular process employed. The degree of adsorbability of gases on charcoal is generally higher for the gases of higher molecular weight. There appears to be a correlation between adsorbability and critical temperature. Thus, gases of low critical temperature, such as hydrogen, nitrogen, oxygen, and carbon monoxide are adsorbed to a lesser degree than gases of higher critical temperature, such as chlorine, sulfur dioxide, hydrogen sulfide, ammonia, nitrous oxide, carbon dioxide and the like. Among the hydrocarbons there is a marked increase in adsorbability with increase in molecular weight. Thus, the process may be employed for the separation of hydrocarbon vapors of higher molecular weight from those of lower molecular weight, as in the adii sorption of natural gasoline from natural gas. It may also be used for purification or concentration of readily adsorbable gases, such as those shown from mixtures in which they are contained.

The ratio of charcoal to feed gas required depends on the proportion of rich gas or highly adsorbable components in the feed and the degree of removal desired. As a possible explanation of its action, it appears that charcoal has a definite adsorptive capacity for each component of a gaseous mixture at a given temperature which capacity is affected only slightly by the operating pressure. Vhen a given amount of fresh charcoal is contacted with feed gas, the charcoal adsorbs all components of the gas to at least a slight degree. Its capacity to adsorb the least readily adsorbable constituents of the gas is soon exceeded, however, and thereafter it will not adsorb further amounts of these constituents, but will continue to adsorb the more readily adsorbable components. As it approaches its adsorptive capacity for each more readily adsorbable component, there is a dei-lnite displacement of the less readily adsorbable material by the more readily adsorbable material. Thus, for a feed gas containing C1 to C4 hydrocarbons including butadiene, mixed with nitrogen, the use of a high ratio of charcoal to feed gas would result in more complete recovery of total hydrocarbons as make gas, and the use of a limited amount of charcoal would result in the production of a smaller amount of a make Jgast-lof higher Ci hydrocarbon or butadiene con- There are many modications of the apparatus design which have not been described above which may be employed without departing from the spirit or scope of the present invention which is directed primarily to a method of stripping 'the enriched adsorbent and not to the me- `eous mixture with a moving bed of granular solid adsorbent so as to cause adsorption of the more readily adsorbable components, separating the unadsorbed components of said gaseous mixture from the enriched adsorbent and stripping the adsorbed components from the enriched adsorbent, the improvement comprising stripping the adsorbed components from the enriched adsorbent in a plurality of stages whereby in'one stage the enriched ladsorbent -is heated to stripping temperatures and contacted fwith relatively small arr'rounts of stripp-ing'gas*and inI a subsequent stage the heated and partially stripped 4adsorbent fcontac-'tdwith relatively large quantitles of the same stripping gas. 2. In a continuous processior the separation 'of gaseous mixturesiby selective adsorption 'an'd desorption accomplished by contacting' Vsaid gas'- e o us mixtures with 'a moving bedoi `fgranular soli-d adsorbent Aso as-to cause adsorptiono lthe more readily adsorbable c'omponents[separating the @adsorbed'sompehenisfef'said"gasees 11i-iii'- ture from `the Yenriched adsorbent, heating" and stripping the adsorbed components `from theehriched adsorbent, cooling thestrippedadsorb'ent to a temperature o f adso'rpion,l and returning cooled strippedadsorb'ent to the adsorption vstage of the process, the improvement comprising two- 4stage stripping vwhereby in ,the initial stage'the Venriched adsorbent is heated to "stripping temperatures andcountercurrently contacted with relatively sniall amounts of strip-ping VYgas and in ,the second Stage the heated and' partially stripped adsorbent is contacted with relatively iargequantities of the same stripping gas.

f3. lnnacontinuous lproc'ess'for the separation of V a gaseous mixture into 'at least three fractions vby selective adsorption anddesorption ac- QQmplished `by contactingsaid mixture with a moving Abed `of granular solid adsorbent so as to canse ,adsorntin @fthe mre readily adsorbable components of said gaseous mixtureby the asl;- sorbent separating the unadsorbed components from Athe enriched adsorbentasa primalfylfrac'- tionv of said gaseous mixture, desorbinga secondaryiiraotion oftheadSQrbed component from the enrichedadsorbent bycontacting said enriched 4ses@ment .with a tertiary' fraction of' saidgasoiis mixture, separating the thus desorbed secondary fraction ofsaid gaseous mixture from thea orbsnt. :Stripping thetrtiarv fraction-of said gasleous mixtureirom the adsorbent, causing' a ppption-,efTthegresultantf-Stripped tertiary fraction to flow countercurrently t 'the downwardly owing bed of granuiar zadsorbent to affect the selective desorption of saidsecondary fraction of said gaseous `mixture and the selective' adsorpt-io'nfof said tertiary fraction of said gaseous mixture on the downwardly flowing adsorbent, separating ing two-stage stripping whereby in theinitial stage the enriched'ad's'orbent is heated 'tostripping temperaturesV and countercurrently contacted with relatively small amounts of stripping gas and in the second stage the heated and partially stripped adsorbent is contacted with relatively large quantities oi the same stripping gas.

4. A process according to claim l wherein the granular solid adsorbent is activated charcoal.

5. A process according to claim 1 wherein the stripping gas is steam.

6. A continuous process for the separation of gaseous mixtures by selective adsorption and desorption which comprises contacting said gaseous mixture with a moving bed of granular solid adsorbent so asito cause adsorption of the more readily adsorbable components, separating the unadsorbed components of said gaseous mixtures from the enriched adsorbent, heating said enriched adsorbent while contacting with relatively 'fthe'e'dsorbgn andrew.

small amounts of stripping gas and subsequently contacting' said" heated adsorbent with relatively large quantities of 'th'esam'e vstrippin'ggas.A "'7'. A continuous processior then separation of a gaseous 'mixture into' at least' three 'fractions which comprises contacting said mixture with' 5a mei/ling bed lof `granul'ar '.'s'o'lid 'adsorbent' 'contained in an adsorption column so 'as' to cause adsorption for-the' more readily ads'orb'able' components o i rsaid gaseous'rnixtur'e the' adsorbentg'separating theunfadsorbdcomponents from the enriched adsorbent as aprin'ifa'r'yr'ac'tionof said mixture', desorbing a" secondary fraction ofthe adsorbed components from' the enriched adsorbent iby"cor-ii'factingv said enriched adsorbent vliifitn ya tert ry tion `of said ig'as'eou's'mixture, separating'the thus'd'esorbed secondary 'fraction of said gaseous miic'tu're from theadsorbent, stripping 4the tertiary raC-ti'onoi'said lgaseous mix'- ture from 'the`adsorbent by heating Asaid enriched adsorbent whileA it' is' moving continuouslydown- 'wa diy countercurrentl-y to a 4compar'atively'small duantity'oi strip'p'inggas and subsequently passin'gfsaid lheated vstd sorbent 'countercurrently to a com-parativeiy largey qila-'ntity of strippin'ggas.Y

c.' A process according to-cmme 'in which the solid adsorbent is activatedcharcoal. '5 9. FAprooss 'according vto' claim 6 in which the Stripping'leas is steam? 10. ,Arrcessaccodins t0 @lem the adsorbent as activated charcoal.

,1.1,- .Arroces a'c'or'dins @claim 7 in which Strippin'geas :1S Steam- 121A'. ,continuons ,proeess for ,the .recovery lof C2 I hydrocarbons' 'fregi a 'gaseous' mixture' which alsolcopta'ins 'other gaseous"'hydroarbns 0f 'lower 'andhifghr' molecularweight than' said C2 ,hydroc bonsA as well fas' 'nori-hydrocarbon y 'gases which Y comprises contacting said mixturev with ajmovingfbedfpf granular solid adsorbent contained naisrstion @plugin S0 as' tto' .cause adsorption of 'the ino're' readilyadsorbable ycoinponents of said Vga ous mixturefbyfthe adz sorbent. afinar from the enrich i .'Czihydrocarbonsfs va rat'i1 fg' thev thus' desoibed secondary' 'fraction'of said gaseous niixture from Y '111s Seid .,Samidarfrwtion frm'said adsorption column; 'stripping' the tertiary fraction of said gaseous mixture from the adsorbent by heating said enriched adsorbent while it is moving continuously downward countercurrently to a stream of stripping gas passing therethrough and subsequently passing said heated adsorbent countercurrently to a relatively large quantity of stripping gas.

13. A process for stripping adsorbed material from a solid adsorbent which comprises passing said adsorbent successively through two stages of a stripping zone, countercurrently contacting said adsorbent in the first stage with a relatively small amount of a stripping gas while simultaneously subjecting it to indirect heating so as to strip a portion of said adsorbed material therefrom, and contacting the resulting adsorbent in the second stage with a relatively 11 large amount of the same stripping gas in the absence of indirect heating so as to strip additional adsorbed material therefrom.

14. A process according to claim 13 in which the stripping gas flows countercurrently to the adsorbent in both stages.

15. A process according to claim 13 in which the portion of adsorbed material stripped in the sec-ond stage is withdrawn separately from the portion stripped in the first stage.

16. A process according to claim 13 in which the stripping gas is steam.

17. A process according to claim 13 in which the second stage is operated at a lower maximum temperature than the first stage.

18. A process according to claim 13 in which hot flue gases are employed to supply the indirect heating, and a separate stream of steam is employed as the stripping gas.

19. An apparatus for stripping adsorbed material from a solid adsorbent which comprises a vertical vessel having a substantially uniform cross sectional area and containing an upper stripping' section and a lower stripping section, gas disengager means at the top of the upper section to permit said adsorbent to pass continuously downward by gravity into said section while separately removing gas therefrom, means for indirectly heating the adsorbent in the upper section, gas disengagermeans between the upper and lower sections to permit said adsorbent to pass continuously downward by gravity therethrough while removing gas therefrom, and gas disengager means at the bottom of the lower section to permit said adsorbent to pass continuously downward by gravity therethrough while introducing stripping gas therein, each of said gas disengager means comprising a horizontal plate extending over the entire cross sectional area of the vessel and having numerous perforations to permit substantially uniform now of solids across the entire cross sectional area.

20. An apparatus according to claim 19 in which each perforation is equipped with an open tube depending from the plate.

21. An apparatus for the separation of gaseous mixtures by selective adsorption and desorption in the moving bed of granular adsorbent which comprises a vertical adsorption column of substantially all uniform cross section provided with a cooling section, an adsorption section, and a stripping section, said stripping section comprising an upper stripping section and a lower stripping section, gas disengager means at the top of the upper section to permit said adsorbent to pass continuously downward by gravity into said section while separately removing gas therefrom, means for indirectly heating-the adsorbent in the upper section, gas disengager means between the upper and lower sections to permit said adsorbent to pass continuously downward by gravity therethrough while removing gas therefrom, and gas disengager means at theA bottom of the lower section to permit said adsorbent to pass continuously downward by gravity therethrough while introducing stripping gas therein, each of said gas disengager means comprising a horizontal plate extending over the entire cross sectional area of the yvessel and having numerous perforations to permit substantially uniform iiow of solids across the entire cross sectional area. 1

22. Ansapparatus for the separation of a gaseous mixture by selective adsorption and desorption in a moving bed of granular adsorbent which comprises a vertical adsorption column of substantially uniform cross section provided with a k,cooling section, an adsorption section, at leastftwo rectification sections, and a stripping section, said stripping section comprising an upperstripping section and a lower stripping section, gas disengager means at the top of the upper section to permit said adsorbent to pass continuously downward by gravity into said section whilev separately removing gas therefrom,`

means for indirectly heating the adsorbent in the upper section, gas disengager means between the upper and lower sections to permit said adsorbent to pass continuously downward by gravity therethrough while removing gas therefrom, and gas'.disengager means at the bottom of the lower section to permit said adsorbent to pass continuously downward by gravity therethrough while introducing stripping gas therein, each of said gas disengager means comprising a horizontal plate extending over the entire cross sectional `area of the vessel and having numerous perforations to permit substantially uniform iiow of solids across the entire cross sectional area.

DONALD H. IMI-IOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,422,007 Soddy July 4, 1922 1,617,960 Muller Feb. 12, 1927 1,825,707 Wagner, Jr. Oct. 6, 1931 1,836,301 Bechthold Dec. 15, 1931 1,872,080 Harris Aug. 16, 1932 

